Irrevocably Happy
by ButterFlight
Summary: It didn't matter that tomorrow might just be his last day on Earth. Because for the first time in a while Eren Jaeger was truly and irrevocably happy.


**I do not own Attack onTitan.**

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Eren lay exhausted on his thin mattress in the basement of the old castle. Ever since he had joined the Scout regiment his training schedule had been extensive and grueling. His muscles ached from day after day of transforming into titan form and testing his limits. Although he'd hate to admit it, if he didn't get a day off soon he feared he might push himself to far.

Anger rose in the pit of his belly. Fists balled, jaw clenched. _What am I thinking? There isn't time for a day off. The titans could attack at any moment. I'll have my day off when every last one of the damned titans are dead! _

While anger usually fueled his fight, tonight Eren was too tired. He slowly began to relax his body.

Stretching on the bed in an attempt to loosen his sore muscles, Eren winced. _Damn it! Hurts more than I thought. _He closed his eyes and focused on his breathing. In and out. The soft rise and fall of his chest felt soothing. Each time his lungs filled with the damp air he would sink a little bit deeper into the worn mattress.

Up above there was the faint sound of people scuttling about the interior of the ancient castle. If he listened close enough he could tell who was moving about by the way they walked. But after today, the only thing Eren cared about was getting some sleep.

He had hardly been able to stay awake during supper. Granted there wasn't any stimulating conversation going on to distract him from his fatigue. After finishing his soup and bread Eren excused himself and headed to wash up. Minutes later he was lying in bed dwelling on the thought of seeing his friends again soon.

_Armin. Mikasa. How long has it been since we last spoke?_ A wave of nostalgia washed over him as he remembered the past. _I don't know what's worse. Facing the titans head on and with our comrades being devoured by mindless beasts or being a prisoner inside the walls for the rest of our lives? _Eren's stomach began to twist into knots. He grimaced, desperately trying to change his train of thought.

At some point during his inner monologue a pair of feet had been making their way down the flights of stairs leading to the basement.

Confident, precise footsteps. Levi.

_What could he possibly want with me at this hour?_

Eren held his breath. Another pair of feet. Light steps, practically nonexistent yet still as precise as the previous pair. _Who is that? It sounds so familiar…_

The steps grew louder as the bodies approached, suddenly coming to a halt outside of the basement door. A few seconds of silenced passed as Eren felt the need to breathe press against his straining lungs. He sucked in a greedy breath right as the key entered the lock and turned with a sharp twist, allowing the door to swing open.

"Jaeger!" a calculating voice called from the shadows. It was most certainly Levi. Eren rose to salute his superior. Levi acknowledged this and signaled him to stand at ease.

The dim flicker of candles bounced off the walls, illuminating the small space with a warm glow. Levi stood at the edge of the light, partially submerged in shadows. A silhouette of a person stood behind him. Curiosity began to ebb away at Eren's state of exhaust. His pulse quickened as he awaited further information from the shorter man.

Levi stood motionless for a few moments assessing Eren's physical state. After he considered several different options he came to a decision. "Jaeger. Tomorrow you will not train. Hange will be here in two days from now to collect you to run some tests. You must be in top physical condition when she arrives. You will rest tomorrow to reserve your strength and heal your body." Levi's sharp gaze never left Eren's frame.

In the back of his throat the young soldier felt a protest clawing its way out but he thought better of it when he felt Levi's gaze drop the room's temperature by ten degrees.

"Yes sir!" he responded with his fist over his heart in the proper salute. Levi nodded and began to exit when realized that their guest was still behind him.

"Jaeger, you have company. They will stay with you over night and will abide by the same rules that you follow." Eren's expectant eyes widened when he saw none other than Mikasa step out of the stairwell's shadows.

_Mikasa!_

For the second time this evening he couldn't speak. _Why was she here? _

Levi took one last look at the pair before turning on his heel for his departure. Even after the click of the lock sounded and the footsteps faded away, silence still engulfed the room.

_Mikasa why are you here? Did something happen behind Wall Rose? Where is Armin? Is he safe? _The questions swirling inside Eren's mind left him speechless.

"Eren!" Mikasa called out before running over and pulling him into a tight, affectionate hug.

He couldn't speak. This was all too strange. _Why would Mikasa be out here? I've missed her so much and all I can think about is what brought her here._

"Eren?" she questioned. "What's wrong? Speak to me.

He shook off the storm of questions inside his head and pulled Mikasa back into a hug. "Mikasa, I've missed you and Armin so much!"

A slight smile graced Mikasa's lips as she savored the touch of her hero. "We've missed you too, Eren."

The pair of friends sat across from each other on the little bed as Mikasa explained the reason for her unexpected visit.

"Levi arranged for it."

_Odd. _While Eren knew Levi could be a gentle, supportive individual it didn't usually show unless someone was about to face certain death.

Then it dawned on him. _Hange's experiment. I'm not going to survive it. Levi said it was a big experiment but he didn't mention that it would cost me my life. I can't die now! Not until I've killed every last titan! Not until I see the world outside these God forsaken walls that have trapped us like cattle!_

"Where's Armin?" Eren pressed with a new sense of fervor.

A hint of sadness and anger reflected in Mikasa's eyes. "I asked to come alone."

Rage started to bubble inside Eren once again. His expiration date had been stamped across his forehead and Mikasa denied him his last chance to see his first true best friend before his death all because she wanted to come alone.

"Mikasa!" Eren yelled. There was something else in his eyes as he lunged for her. Something so fragile yet wild. Something that not only fueled his anger but controlled him.

For the first time in years Mikasa looked into Eren's eyes and saw fear in its purest form.

Those teal eyes shined with emotion. It was beautiful and terror-ridden causing Mikasa's heart to thud rapidly in her chest. Just as he was about to tackle her off the bed, she grabbed his wrists in on swift movement and pinned him to his mattress. Hovering over his body before he had the time to react, Mikasa pressed her lips to the center of his forehead. Tears threatened to spill over the rims of her grey eyes.

Eren immediately froze.

"Mi-Mikasa?"

She pulled away and stared down at her adoptive brother. After a few shaky breaths she composed herself. "I can't let you leave me, this world, without knowing the truth."

Before Eren could protest, Mikasa leaned down firmly planting her lips on his.

Eren's eyes pinned open with shock stared at Mikasa as she kissed him. After no response from Eren's side of the kiss Mikasa broke away and looked down.

"Mi-Mikasa, why?" A mix of surprised and confused tones riddled his voice.

Mikasa flinched slightly at his question but soon met his eyes with a calm resolve.

" Eren, I may be a sister in your eyes but I have thought of you as so much more than just a brother. You are my hero and my best friend. The one who showed up when all hope was lost and you told me to fight. " Tears began to slowly spill over. "And I'm not ready to face this world without you. I don't want to fight without you."

Eren sat dumbstruck starring back at the girl he had saved so many years ago. _It shouldn't have to be this way. I can't die now. I can't. Mikasa needs me. Armin needs me. And I need them. God damnit Hange! I will not die in your experiment! I am not a lab rat! I am a human being! I will persevere. For Armin. For Mikasa. For the survival of humanity. For freedom._

Eren had become tense during his stream of consciousness. Noticing this, Mikasa gently held his hands until he became aware of his surroundings once again. He met her sad eyes and released his hands only to reposition them on top of hers.

With a new resolve, "Mikasa, I'm not going to leave you. Not without a fight." He squeezed tighter. "Hange's experiment will not be my imminent death. I shall prevail until every last titan has been killed and we are free from these treacherous walls."

Silence. Then Mikasa closed her eyes and nodded.

Eyes still closed she spoke in a hushed tone. "Eren, before Hange reaches you, I-I…"

She stuttered.

"What is it Mikasa? Tell me." Teal orbs focused intently on the usually confident girl. _I don't think I've ever seen her this nervous before._

"Eren will you be mine entirely?" she spat out.

Not understanding the question. "Of course Mikasa. I already am."

A series of shallow breaths passed through Mikasa's lips before she figured out how to rephrase her request. "No, Eren. I mean entirely."

He still wasn't getting it.

She took a deep breath, "I-I want you to have me first."

Realization spread like wild fire over his features as the request finally sunk in. _Mikasa wants me to—_He shook his head. After all she couldn't possibly mean—

"Eren!"

Mikasa's expectant eyes met lost ones. "Please." She murmured more to herself than anyone else.

Eren swallowed, "Mikasa, a-are you sure?" There was a new sensation in his stomach now comparable to the fluttering of trapped insects.

A few seconds passed. "Yes."

Her response triggered a primal need deep within him. Eren leaned forward capturing her lips in a chaste kiss. Mikasa immediately responded by pushing Eren back against his bed.

A tongue demanded entrance as it prodded Mikasa's lips. She granted this wish with an open mouth and the kiss deepened. Eren's tongue was sloppy and unskilled. But Mikasa did not mind one bit. Eren hesitated briefly before placing his hands on the small of Mikasa's back and then began to slowly run them up and down her sides.

Mikasa pulled away gasping for breath. A trail of spit connected their lips and both teens blushed visibly. Mikasa sat up on Eren's lap, reaching for the buttons on her shirt when Eren stopped her.

"Allow me." A larger pair of hands pulled at the buttons, undoing them one by one until a landscape of smooth ivory skin was displayed. He eased her shirt off of her and paused, taking in the sight of his friend's almost bare chest. The muscles in her abdomen were far past well defined.

Mikasa reached for the hem of Eren's shirt and pulled it over his head with little resistance. His torso was perfectly chiseled dipping into a sharp V-shape that disappeared beneath the line of his pants.

Eren leaned in feathering Mikasa's jaw in soft, wet kisses. Once he reached her left ear, he moved down to her neck and lightly suckled on her pulse. Mikasa's breath hitched and a gentle mewl escaped her throat. Eren smiled into her neck, nipping at it to extract another sound. And that he did. Another soft moan slipped past Mikasa's defenses as she began to melt further into his body.

Eren now moved away from her neck, kissing his way across her collarbone and over to her shoulder. As he did this, he began to fiddle with the clip of her bra.

Once the clasp unclipped and the straps loosened, he started to remove the garment when Mikasa stopped him. Holding it firmly to her chest, nervous grey met a worried teal.

_Oh God…. Have I gone too fast?_

Eren reached down and gave her hand a soft squeeze, reassuring her that whatever she decided would be fine with him. Mikasa nodded and a relieved smile spread across her face. She discarded the article of clothing and waited for his reaction.

She hadn't realized she had been closing her eyes until she opened them to see Eren gazing lovingly at her breasts.

"Beautiful. You are absolutely beautiful, Mikasa." Eren carefully reached out to cup her perky, cream-colored mounds.

She leaned into his touch as the pads of his thumbs rubbed gentle circles over her pert nipples. He went back to sucking on her pulse then slowly kissing down her collarbones to her chest where he took a single nipple into his mouth and suckled. Mikasa gasped as she felt a wet appendage tease her breast. Eren's hands moved to guide her body into a laying position.

Once on top, Eren continued his trail of kisses sending sparks through Mikasa as he went until he reached the button of her pants. He stopped, hooking his fingers underneath the top and looked up at Mikasa.

Mikasa's head was leaned back and her eyes shut. She looked so peaceful like this.

"Mi-Mikasa?"

She snapped out of her daze and locked eyes with Eren. All of the sudden she became extremely aware of their current position. She reached down and placed her palms atop his hands and squeezed lightly. Then in one swift movement she unbuttoned her pants and they sagged open revealing a pair of plain-looking underwear.

Eren tugged her bottoms off, leaving he panties in place. After discarding them to the floor, he undid his own pair and slipped out of them. The lack of pressure made Eren release a pleasured sigh. Mikasa could now see a clear outline of Eren's erection through his undershorts. Before Eren could climb on top of Mikasa again she sat up and pulled him down. The next thing Eren felt was a new pressure being firmly applied to his crotch. He let out a guttural groan as Mikasa slipped her hand underneath the thin fabric.

Mikasa's grasp only became firmer as she slowly pumped him. _Too firm. How do I tell her?_ Eren winced visibly and Mikasa halted her ministrations.

"Eren?" Concern filled her grey eyes.

_Oh God. What do I say?! _Eren swallowed.

"Too tight." He mumbled. Mikasa's face dropped. "But what you were doing before felt amazing, really!" he quickly added.

Eren wrapped his hand around Mikasa's with an appropriate amount of pressure and guided it up and down his length.

"Hng!" _Getting too close. Not yet._ He stopped their hands and turned his attention onto her. "Mikasa, this might hurt you a little bit. Let me make you more comfortable."

Mikasa nodded and lay back on the mattress. Eren ignored his straining erection and focused on pulling Mikasa's last article of clothing off. Her panties were a little damp. Eren leaned down and kissed the center of her pubic bone before carefully prying her legs apart. A part of him wanted nothing more then to fill her this very instant but he knew better.

Eren lowered his head into the space right between her legs and drew is tongue firmly across her lips. Mikasa shuddered. The knots deep in her belly were stirring. The level of ecstasy that she was feeling in this moment was immense.

Eren's tongue relentlessly assaulted her core where in the midst of his work he found a little nub that sent a tingling sensation racing up Mikasa's spine.

"Eren! I can't hold out much longer."

Eren promptly stopped his work and stood up to remove his bottoms. The touch of the fabric reminded him of how hard he really was. As he settled between her legs he reached up and found one of Mikasa's hands, grasping it as he braced himself with his other arm.

Mikasa reached down and slowly guided his length to her entrance.

Concentration locked on to Eren's face as he pushed into her warm folds. She was dripping with fluids from their previous activities that only made it harder to pace himself.

_For Mikasa. This about Mikasa. Be gentle for her sake._

The dull ache he felt in his member before was now throbbing. He had pushed about half of himself inside when Mikasa took in a sharp breath. Eren froze.

"Keep going." She whispered through gritted teeth. He nodded and pushed the rest of himself inside, filling her to the hilt. Her heat engulfed him completely. He could hardly remain still. He was panting heavily when Mikasa gave him the cue.

"Move Eren." With another nod, he pulled himself out three quarters of the way and slid back in. This pattern continued slowly until Mikasa's hips began to meet his own and the beautiful girl below him began to moan in expectation.

Eren picked up the pace with his thrusts. Mikasa's accuracy and excellent timing matching him effortlessly and they were both seconds away from release.

Eren reached down and rubbed Mikasa's little bundle of nerves furiously as she captured his lips in a sloppy, needy kiss.

They caught their names in each other's breath as they spilled over the edge simultaneously. Mikasa's hips shook violently as Eren filled he with his own juices.

Eren collapsed on top of Mikasa as the ending of his orgasm was wrung out of him. "Mikasa. I'm glad it was with you."

She smiled at this as Eren removed himself from her.

"Me too, Eren. Thank you."

Eren matched her smile and the two teens drifted off into a comfortable sleep. It didn't matter that tomorrow might just be his last day on Earth. Because for the first time in a while Eren Jaeger was truly and irrevocably happy.


End file.
